Enable Custom Metrics App Config Value

[nharper285]

Summary of the Pull Request

What is this about?
EnableCustomMetrics was set to 'false' by default so it was getting reset every release.

PR Checklist

• Applies to work item: #xxx
• CLA signed. If not, go over here and sign the CLI.
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Info on Pull Request

What does this include?

Validation Steps Performed

How does someone test & validate?

[codecov-commenter]

Codecov Report

Merging #3190 (5551da4) into main (aa54a15) will decrease coverage by 0.77%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3190      +/-   ##
==========================================
- Coverage   29.57%   28.81%   -0.77%     
==========================================
  Files         332      174     -158     
  Lines       39056    21349   -17707     
==========================================
- Hits        11552     6152    -5400     
+ Misses      27504    15197   -12307     

see 189 files with indirect coverage changes